How to Know Which Optocoupler to Buy

Hardware
1

I’m connecting wired door and window sensors to ESPHome and based on all of my reading am going to add optocouplers. I understand why I need one, but most of the details of how they work is a bit of a mystery to me.

When shopping for them, there are different “sizes.” How do I know which to buy? Is the first number the power supply voltage and the second number ESPXXXX voltage?

Thanks.

2

Doesnt matter very much which one you chose. What’s important that it runs on 3.3/5v and that it can handle the current that goes through it. Digi Key or Farnell have great websites for this